Stockholders' Equity - Summary of Stockholders' Equity (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class A Common Stock
Class Of Stock [Line Items]
Common stock, shares outstanding, beginning balance	2,419,107	2,411,107	2,404,107
Issued	7,000	8,000	7,000
Common stock, shares outstanding, ending balance	2,426,107	2,419,107	2,411,107
Class B Common Stock
Class Of Stock [Line Items]
Common stock, shares outstanding, beginning balance	10,000,000	10,000,000	10,000,000
Common stock, shares outstanding, ending balance	10,000,000	10,000,000	10,000,000